The present invention relates to flowline risers, more particularly to top tensioned import/export flowline risers for a tension leg platform (TLP), for testing and producing hydrocarbon formations in offshore waters.
A top tensioned riser (TTR) takes advantage of the TLP's superior motion characteristics to provide cost-effective flowline risers. In deepwater, import/export risers would typically be of the steel catenary riser (SCR) type in which the pipeline is supported at a riser porch near keel level of the TLP and takes an arched or catenary path to the touchdown point or connection on the seabottom. As water depth and/or diameter of the SCR increases in deepwater, its weight and cost increases significantly. The SCR extends outwardly from the TLP where it is supported at its upper end. Due to the proximity of SCRs and tendons anchoring the TLP to the seabottom, interference between risers and tendons must be carefully analyzed and managed during installation and operation.
It is therefore an object of the present invention to provide a riser that avoids tendon interference.
It is another object of the present invention to provide a top tensioned riser extending substantially vertically from the seabottom.
It is another object of the present invention to provide a top tensioned riser incorporating length adjustment.
It is yet another object of the present invention to provide a top tensioned riser incorporating riser tension monitoring means.
It is another object of the present invention to provide a top tensioned riser without active motion compensation.